1. Field of the Invention
This invention relates to thickened aqueous scouring cleansers containing abrasives and more particularly to such cleansers which are formulated to exhibit plastic rheologies and which exhibit substantially no syneresis.
2. Description of the Prior Art
In the guest for hard surface cleaners which have efficacy against a variety of soils and stains, various heavy duty abrasive-containing and/or thickened cleansers have been developed. As an example, U.S. Pat. Nos. 3,985,668, 4,005,027 and 4,051,056 all issued to Hartman, show a combination of perlite (an expanded silica abrasive, which is here used as a filler), a colloid-forming clay, in combination with a hypochlorite bleach, a surfactant and a buffer in which abrasives are suspended. A clay thickened system of this type tends to set up or harden upon storage due to the false body nature of the thickneners, and require shaking before use to break down the false body structure. Beyer, U.S. Pat. No. 4,235,732 also describes a bleaching cleanser, including a clay suspending agent to result in a false-bodied fluid. Other prior art cleaners which attempt to suspend abrasives use either inorganic colloid thickeners only or mixed surfactant thickeners at high levels of surfactants. Additionally, syneresis becomes a problem as the solids portion of such cleansers substantially separate from the liquids portion. One approach to alleviate this is to use a perlite type material with specified particle size as defined in Hartman. High levels of surfactants can be used to form a rheology favorable for the suspension of abrasives. These mixed surfactant thickened compositions, shown for example, in U.S. Pat. Nos. 4,352,678, and 4,588,514 issued to Jones et al, have been used to suspend abrasives and to incorporate a source of hypochlorite bleach. However, Jones et al require large amounts of expensive surfactants in order to suspend abrasives, and do not provide a particularly use favorable rheology.
U.S. Pat. No. 4,287,079, issued to Robinson, relates to a clay/silicon dioxide thickened, bleach-containing abrasive cleanser which could contain an anionic surfactant. Due to the clay-thickened rheology, cleansers of this sort quickly dry out and set up. These types of cleansers become less flowable over time, and are also plagued by significant syneresis problems. U.S. Pat. No. 3,956,158, (also British Pat. No. 1,418,671) issued to Donaldson shows an abrasive-containing bleach thickened with insoluble detergent filaments. It has been surprisingly found that calcium carbonate (CaCO.sub.3), used as an abrasive in many prior art formulations, greatly accelerates the syneresis process in compositions having alkali-metal silicates and bicarbonates.
Other patent references disclose or suggest the use of borax, borate or perborate as an electrolyte or buffer in an abrasive cleanser. These include U.S. Pat. Nos. 4,599,186, and 4,657,962 issued to Choy et al, which describe an alumina-thickened cleanser without substantial syneresis and including SAS and LAS surfactants, sodium silicates and calcite. U.S. Pat. No. 3,850,833 issued to Koceich et al, comprises a calcium carbonate abrasive, LAS and alkane sulfonate surfactants, sodium silicates and borax. Bechtold U.S. Pat. No. 3,860,525 includes ethoxylated alcohol surfactants, sodium silicates and borax. Moore, U.S. Pat. No. 3,530,071 includes a calcium carbonate abrasive, LAS surfactant, sodium silicate and borax as a stabilizer for a chlorinated TSP bleach. Puryear, U.S. Pat. No. 4,248,728 describes an abrasive hard surface cleanser thicknened with a colloidal magnesium aluminum silicate clay to result in a thixotropic rheology. Puryear also includes sodium metasilicate, a hypochlorite bleach, a calcium carbonate abrasive and may include LAS, SAS and ethoxylated alcohol surfactants, bicarbonates and borates. Puryear, however operates in a relatively high pH range (11-14) and the magnesium aluminum silicate requires heating, or the application of high shear, during production to achieve the rheology. U.S. Pat. No. 3,444,254 issued to Suiter describes a borax/sodium-silicate stabilizer for a peroxide bleach.
In view of the art there is a need for a thickened hard surface cleanser which is capable of suspending abrasives, exhibits no syneresis over time, does not require shaking before use and has superior cleaning performance.
It is therefore an object of the present invention to provide a thickened abrasive cleanser with a plastic flowable rheology, which does not have a tendency to set up or harden and exhibits substantially no syneresis.
It is another object of the present invention to provide a thickened cleanser which can stably suspend abrasives.
It is another object of the present invention to provide a thickened hard surface cleanser with demonstrated cleaning efficacy on oil and grease stains, soap scums, mildew and particulate soils.
It is yet another object of the present invention to provide a cleanser with sufficient viscosity and yield value to adhere to non-horizontal surfaces.